Demographic Math

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Transcript Demographic Math

Demographic math
Two things you will be able to do at
the end of this lesson:
Calculate a population’s doubling
 Predict future population size
Please get out a calculator
Doubling time
Formula: Time =70
r= growth rate
Example: a country is growing at 2%
a year. In how many years will the
county’s population double?
The Ivory Coast is growing at 3.8%
each year. In how many years will it
 China is growing at 1.2%. In what
year will China’s population be
double what it is today?
Calculating future population
A = Pert
A = future population size
 P = current population size
 Constant e = 2.72
 Growth rate r reported as percent of
 T = time
A = Pert
Try one!
 The US population this year is 306
million and our growth rate is .6%.
How large will the population be in
Try another one! 
The world’s population is about 677
million and our growth rate is 1.2%.
Assuming the rate stays constant,
how big will the population be by
2050? By 2100?
Check for understanding
What two calculations did you just
learn how to do?
 What can you use A = Pert for?
 Which equation is simpler?
 What is the common mistake that is
made in the A = Pert formula?